1. Field of the Invention
The present invention relates to a printing apparatus and reading apparatus for a watermarked document in which secret information is embedded by an electronic watermarking technology or the like, a print processing system in which the pieces of apparatus are used as a system component, and a print processing method.
2. Description of the Related Art
In modern-day society, trading is widely performed through “document” such as various application forms and a certificate. Sometimes the documents are dealt with in a form of a digitized electronic document. On the other hand, a printed document has advantages and ease of handling with not shared by the electronic document. This is attributed to the fact that the advantages of the printed document such as low cost, a good glance at the document, ease of carry, and ease of distribution are widely accepted when compared with the electronic document in which a personal computer or the like is required to browse the document. In the printed document, there is a technique of embedding the secret information by the electronic watermarking technology. The technique is used in a variety of applications such as management of the printed document to which digital information is added and detection of printed document tampering.
Usually, in the printed document, in which the secret information is embedded by the electronic watermarking technology, the secret information is obtained by reading the document with a scanner, or a process of detecting the secret information tampering is performed by comparison with information on contents of the original document. However, there is a possibility that reading failure is generated by a temporal malfunction of the scanner. Sometimes the reading failure is generated in the case where a wrinkle or a stain remains on paper. Sometimes printing density is destabilized due to a small amount of toner on a printer side, which leads to fail to read the embedded information.
The reading failure is also a possible problem that occurs in an electronic watermark information reading operation in a copying machine equipped with an electronic watermark reading function. The same problem is also generated, aside from the document, in techniques of printing and reading an image in which the secret information is embedded (for example, see Japanese Patent Application Laid-Open Nos. 2001-157022 and 2002-64700). In addition, the same problem is possibly generated in a barcode system or two-dimensional barcode system, in which the information is printed on paper in the form of an image pattern read with a device.